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Code Illustrating Hashes and Related Syntax

Hash Assignment
Hash Element Access
exists ( $hash{$key} )
keys( %hash )
delete ( $hash{key} )
values( %hash )
each( %hash )
Make an "Inverse" Hash
Let's Expand Our Real-World Example...
Visualizing a Hash Structure with FakeHash
A List of Hash Resources

Some Very Simple Code Illustrating Hashes and Related Syntax

#! /usr/local/bin/perl -w # # these are very simplistic syntax examples; # there's much more to know, so see the # resources below! use strict; use warnings; use Data::Dumper;
# Hash Assignment # In this case, a # 1 : 1 relationship # key => value my %StateName = ( AK => 'Alaska', AL => 'Alabama', AR => 'Arkansas', AZ => 'Arizona', CA => 'California', CO => 'Colorado', CT => 'Connecticut', DC => 'District Of Columbia', DE => 'Delaware', FL => 'Florida', GA => 'Georgia', HI => 'Hawaii', IA => 'Iowa', ID => 'Idaho', IL => 'Illinois', IN => 'Indiana', KS => 'Kansas', KY => 'Kentucky', LA => 'Louisiana', MA => 'Massachusetts', MD => 'Maryland', ME => 'Maine', MI => 'Michigan', MN => 'Minnesota', MO => 'Missouri', MS => 'Mississippi', MT => 'Montana', NC => 'North Carolina', ND => 'North Dakota', NE => 'Nebraska', NH => 'New Hampshire', NJ => 'New Jersey', NM => 'New Mexico', NV => 'Nevada', NY => 'New York', OH => 'Ohio', OK => 'Oklahoma', OR => 'Oregon', PA => 'Pennsylvania', RI => 'Rhode Island', SC => 'South Carolina', SD => 'South Dakota', TN => 'Tennessee', TX => 'Texas', UT => 'Utah', VA => 'Virginia', VT => 'Vermont', WA => 'Washington', WI => 'Wisconsin', WV => 'West Virginia', WY => 'Wyoming' ); my $href = \%StateName; # reference to the hash %StateName print Dumper $href; # note the order will differ from that + above print "\n";
# hash element access my $State = 'SD'; # planetscape's home state my $Name = $StateName{$State}; print "planetscape lives in " . $Name . "\.\n\n";
# exists ( $hash{$key} ) $State = 'QC'; # Quebec, Canada if (exists($StateName{$State})) { print "The abbreviation for $State is " . $StateName{$State} . "\. +\n\n"; } else { print $State . " is not a state! (yet)\n\n"; }
# keys( %hash ) my $count = keys %StateName; print "There are $count elements in the hash.\n\n"; foreach $State (keys(%StateName)) { print "State abbreviation is '$State'\n"; } print "\n";
# delete ( $hash{key} ) delete($StateName{DC}); # DC is not actually a state, # it's a postal abbreviation
# values( %hash ) $count = values %StateName; # $count is one less since we deleted DC print "There are $count elements in the hash.\n\n"; foreach $State (values(%StateName)) { print "State name is '$State'\n"; } print "\n";
# each( %hash ) while (my($key,$value)=each(%StateName)) { # there's lots more to +know print "key='$key', value='$value'\n"; # about "each" - see the # resour +ces below! } print "\n";
# make an inverse hash my %StateAbbreviation = reverse %StateName; # exists ( $hash{$key} ) $State = 'Quebec'; # QC if (exists($StateAbbreviation{$State})) { print "The abbreviation for $State is " . $StateAbbreviation{$Stat +e} . "\.\n\n"; } else { print $State . " is not a state! (yet)\n\n"; } print "\n";
# let's expand our real-world example from a hash of States # to a hash of postal abbreviations (not exhaustive) my %PostalCode = %StateName; # copy %StateName to %PostalCode $PostalCode{AS} = 'American Samoa'; $PostalCode{DC} = 'District of Columbia'; $PostalCode{FM} = 'Federated States of Micronesia'; $PostalCode{GU} = 'Guam'; $PostalCode{MH} = 'Marshall Islands'; $PostalCode{MP} = 'Northern Mariana Islands'; $PostalCode{PW} = 'Palau'; $PostalCode{PR} = 'Puerto Rico'; $PostalCode{VI} = 'Virgin Islands'; $PostalCode{PW} = 'Palau'; # many more postal codes and abbreviations for the US and Canada # may be found here: +ns.html # and here: foreach my $pc (keys(%PostalCode)) { print "PostalCode for '$PostalCode{$pc}' is '$pc'\n"; }

Visualizing a Hash Structure with FakeHash

FakeHash is a module by Mark-Jason Dominus which was first announced here. I have elaborated slightly on the code presented in order to demonstrate some additional details such as setting drawing parameters. (More info on FakeHash can be found here.)


use strict; use warnings; use FakeHash; my %h = ( When => 1, in => 2, the => 3, course => 4, of => 5, human => 6, events => 7, it => 8, becomes => 9, necessary => 10, for => 11, one => 12, people => 13, ); open( my $FILEHANDLE, ">FakeHashDrawing.txt" ); my $fake = FakeHash::DrawHash->new; $fake->draw_param( 'BUCKET', [1.5, 0.75] ); $fake->draw_param( 'KVP' => [2.0, 0.75] ); while ( my ( $key, $value ) = each(%h) ) { $fake->store( $key, $value ); } $fake->draw($FILEHANDLE); close $FILEHANDLE;

This code produces the following output:

.PS boxwid:=1.5; boxht:=0.75 B00: box boxwid:=1.5; boxht:=0.75 B01: box with .n at B00.s circle at B01.c rad 0.1 filled arrow from B01.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N0100: box "becomes" "9" "134720492145(17)" boxwid:=1.5; boxht:=0.75 B02: box with .n at B01.s circle at B02.c rad 0.1 filled arrow from B02.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N0200: box "necessary" "10" "164114526854434(2)" boxwid:=1.5; boxht:=0.75 B03: box with .n at B02.s circle at B03.c rad 0.1 filled arrow from B03.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N0300: box "human" "6" "131651875(3)" boxwid:=1.5; boxht:=0.75 B04: box with .n at B03.s boxwid:=1.5; boxht:=0.75 B05: box with .n at B04.s boxwid:=1.5; boxht:=0.75 B06: box with .n at B05.s circle at B06.c rad 0.1 filled arrow from B06.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N0600: box "in" "2" "3686(6)" boxwid:=2; boxht:=0.75 N0601: box "people" "13" "4647902198(22)" boxwid:=2; boxht:=0.75 N0602: box "course" "4" "4135697990(6)" boxwid:=1.5; boxht:=0.75 B07: box with .n at B06.s boxwid:=1.5; boxht:=0.75 B08: box with .n at B07.s circle at B08.c rad 0.1 filled arrow from B08.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N0800: box "When" "1" "3344568(24)" boxwid:=2; boxht:=0.75 N0801: box "one" "12" "128504(24)" boxwid:=1.5; boxht:=0.75 B09: box with .n at B08.s circle at B09.c rad 0.1 filled arrow from B09.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N0900: box "events" "7" "4224378201(25)" boxwid:=1.5; boxht:=0.75 B10: box with .n at B09.s circle at B10.c rad 0.1 filled arrow from B10.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N1000: box "of" "5" "3882(10)" boxwid:=1.5; boxht:=0.75 B11: box with .n at B10.s circle at B11.c rad 0.1 filled arrow from B11.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N1100: box "the" "3" "133915(27)" boxwid:=1.5; boxht:=0.75 B12: box with .n at B11.s circle at B12.c rad 0.1 filled arrow from B12.c right boxwid/2 + 0.2 boxwid:=2; boxht:=0.75 N1200: box "it" "8" "3692(12)" boxwid:=2; boxht:=0.75 N1201: box "for" "11" "118444(12)" boxwid:=1.5; boxht:=0.75 B13: box with .n at B12.s boxwid:=1.5; boxht:=0.75 B14: box with .n at B13.s boxwid:=1.5; boxht:=0.75 B15: box with .n at B14.s .PE

Once you have generated FakeHashDrawing.txt with the above Perl code, you can convert it to PostScript with the following (under Cygwin/*nix):

pic FakeHashDrawing.txt | groff -c -Tps >

View the Output

(I then used Jasc Paint Shop Pro 8 to convert PostScript to PNG for display purposes.)

If you prefer a more "modern" standard such as SVG, you can use a utility such as plotutils' pic2plot to convert from Unix pic format to SVG or any other of a wide variety of formats. For example:

pic2plot -T svg FakeHashDrawing.txt > FakeHashDrawing.svg

Produces (on Cygwin):

<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?> <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20000303 Stylable//EN" " +e.dtd"> <svg width="8in" height="8in" viewBox="0 0 1 1" preserveAspectRatio="n +one"> <title>SVG drawing</title> <desc>This was produced by version 4.1 of GNU libplot, a free library +for exporting 2-D vector graphics.</desc> <rect x="0" y="0" width="1" height="1" style="stroke:none;fill:white;" +/> <g transform="translate(0.058854,-0.14453) scale(1,-1) scale(0.11458) +" xml:space="preserve" style="stroke:black;stroke-linecap:butt;stroke +-linejoin:miter;stroke-miterlimit:10.433;stroke-dasharray:none;stroke +-dashoffset:0;stroke-opacity:1;fill:none;fill-rule:even-odd;fill-opac +ity:1;font-style:normal;font-variant:normal;font-weight:normal;font-s +tretch:normal;font-size-adjust:none;letter-spacing:normal;word-spacin +g:normal;text-anchor:start;"> <rect x="0" y="-0.375" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <rect x="0" y="-1.125" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-0.75" r="0.1" style="stroke-width:0.010267;fill +:gray;"/> <line x1="0.75" y1="-0.75" x2="1.7" y2="-0.75" style="stroke-width:0.0 +10267;"/> <polygon points="1.6,-0.725 1.7,-0.75 1.6,-0.775 " style="stroke-width +:0.010267;fill:black;"/> <rect x="1.7" y="-1.125" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-0.56818) scale(1,-1) " style="font-fam +ily:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;basel +ine-identifier:centerline;stroke:none;fill:black;">becomes</text> <text transform="translate(2.7,-0.75) scale(1,-1) " style="font-family +:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline +-identifier:centerline;stroke:none;fill:black;">9</text> <text transform="translate(2.7,-0.93182) scale(1,-1) " style="font-fam +ily:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;basel +ine-identifier:centerline;stroke:none;fill:black;">134720492145(17)</ +text> <rect x="0" y="-1.875" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-1.5" r="0.1" style="stroke-width:0.010267;fill: +gray;"/> <line x1="0.75" y1="-1.5" x2="1.7" y2="-1.5" style="stroke-width:0.010 +267;"/> <polygon points="1.6,-1.475 1.7,-1.5 1.6,-1.525 " style="stroke-width: +0.010267;fill:black;"/> <rect x="1.7" y="-1.875" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-1.3182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">necessary</text> <text transform="translate(2.7,-1.5) scale(1,-1) " style="font-family: +'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline- +identifier:centerline;stroke:none;fill:black;">10</text> <text transform="translate(2.7,-1.6818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">164114526854434(2)< +/text> <rect x="0" y="-2.625" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-2.25" r="0.1" style="stroke-width:0.010267;fill +:gray;"/> <line x1="0.75" y1="-2.25" x2="1.7" y2="-2.25" style="stroke-width:0.0 +10267;"/> <polygon points="1.6,-2.225 1.7,-2.25 1.6,-2.275 " style="stroke-width +:0.010267;fill:black;"/> <rect x="1.7" y="-2.625" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-2.0682) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">human</text> <text transform="translate(2.7,-2.25) scale(1,-1) " style="font-family +:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline +-identifier:centerline;stroke:none;fill:black;">6</text> <text transform="translate(2.7,-2.4318) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">131651875(3)</text> <rect x="0" y="-3.375" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <rect x="0" y="-4.125" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <rect x="0" y="-4.875" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-4.5" r="0.1" style="stroke-width:0.010267;fill: +gray;"/> <line x1="0.75" y1="-4.5" x2="1.7" y2="-4.5" style="stroke-width:0.010 +267;"/> <polygon points="1.6,-4.475 1.7,-4.5 1.6,-4.525 " style="stroke-width: +0.010267;fill:black;"/> <rect x="1.7" y="-4.875" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-4.3182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">in</text> <text transform="translate(2.7,-4.5) scale(1,-1) " style="font-family: +'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline- +identifier:centerline;stroke:none;fill:black;">2</text> <text transform="translate(2.7,-4.6818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">3686(6)</text> <rect x="3.7" y="-4.875" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(4.7,-4.3182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">people</text> <text transform="translate(4.7,-4.5) scale(1,-1) " style="font-family: +'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline- +identifier:centerline;stroke:none;fill:black;">13</text> <text transform="translate(4.7,-4.6818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">4647902198(22)</tex +t> <rect x="5.7" y="-4.875" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(6.7,-4.3182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">course</text> <text transform="translate(6.7,-4.5) scale(1,-1) " style="font-family: +'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline- +identifier:centerline;stroke:none;fill:black;">4</text> <text transform="translate(6.7,-4.6818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">4135697990(6)</text +> <rect x="0" y="-5.625" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <rect x="0" y="-6.375" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-6" r="0.1" style="stroke-width:0.010267;fill:gr +ay;"/> <line x1="0.75" y1="-6" x2="1.7" y2="-6" style="stroke-width:0.010267; +"/> <polygon points="1.6,-5.975 1.7,-6 1.6,-6.025 " style="stroke-width:0. +010267;fill:black;"/> <rect x="1.7" y="-6.375" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-5.8182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">When</text> <text transform="translate(2.7,-6) scale(1,-1) " style="font-family:'H +elvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-id +entifier:centerline;stroke:none;fill:black;">1</text> <text transform="translate(2.7,-6.1818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">3344568(24)</text> <rect x="3.7" y="-6.375" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(4.7,-5.8182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">one</text> <text transform="translate(4.7,-6) scale(1,-1) " style="font-family:'H +elvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-id +entifier:centerline;stroke:none;fill:black;">12</text> <text transform="translate(4.7,-6.1818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">128504(24)</text> <rect x="0" y="-7.125" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-6.75" r="0.1" style="stroke-width:0.010267;fill +:gray;"/> <line x1="0.75" y1="-6.75" x2="1.7" y2="-6.75" style="stroke-width:0.0 +10267;"/> <polygon points="1.6,-6.725 1.7,-6.75 1.6,-6.775 " style="stroke-width +:0.010267;fill:black;"/> <rect x="1.7" y="-7.125" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-6.5682) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">events</text> <text transform="translate(2.7,-6.75) scale(1,-1) " style="font-family +:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline +-identifier:centerline;stroke:none;fill:black;">7</text> <text transform="translate(2.7,-6.9318) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">4224378201(25)</tex +t> <rect x="0" y="-7.875" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-7.5" r="0.1" style="stroke-width:0.010267;fill: +gray;"/> <line x1="0.75" y1="-7.5" x2="1.7" y2="-7.5" style="stroke-width:0.010 +267;"/> <polygon points="1.6,-7.475 1.7,-7.5 1.6,-7.525 " style="stroke-width: +0.010267;fill:black;"/> <rect x="1.7" y="-7.875" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-7.3182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">of</text> <text transform="translate(2.7,-7.5) scale(1,-1) " style="font-family: +'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline- +identifier:centerline;stroke:none;fill:black;">5</text> <text transform="translate(2.7,-7.6818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">3882(10)</text> <rect x="0" y="-8.625" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-8.25" r="0.1" style="stroke-width:0.010267;fill +:gray;"/> <line x1="0.75" y1="-8.25" x2="1.7" y2="-8.25" style="stroke-width:0.0 +10267;"/> <polygon points="1.6,-8.225 1.7,-8.25 1.6,-8.275 " style="stroke-width +:0.010267;fill:black;"/> <rect x="1.7" y="-8.625" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-8.0682) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">the</text> <text transform="translate(2.7,-8.25) scale(1,-1) " style="font-family +:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline +-identifier:centerline;stroke:none;fill:black;">3</text> <text transform="translate(2.7,-8.4318) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">133915(27)</text> <rect x="0" y="-9.375" width="1.5" height="0.75" style="stroke-width:0 +.010267;"/> <circle cx="0.75" cy="-9" r="0.1" style="stroke-width:0.010267;fill:gr +ay;"/> <line x1="0.75" y1="-9" x2="1.7" y2="-9" style="stroke-width:0.010267; +"/> <polygon points="1.6,-8.975 1.7,-9 1.6,-9.025 " style="stroke-width:0. +010267;fill:black;"/> <rect x="1.7" y="-9.375" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(2.7,-8.8182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">it</text> <text transform="translate(2.7,-9) scale(1,-1) " style="font-family:'H +elvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-id +entifier:centerline;stroke:none;fill:black;">8</text> <text transform="translate(2.7,-9.1818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">3692(12)</text> <rect x="3.7" y="-9.375" width="2" height="0.75" style="stroke-width:0 +.010267;"/> <text transform="translate(4.7,-8.8182) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">for</text> <text transform="translate(4.7,-9) scale(1,-1) " style="font-family:'H +elvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-id +entifier:centerline;stroke:none;fill:black;">11</text> <text transform="translate(4.7,-9.1818) scale(1,-1) " style="font-fami +ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli +ne-identifier:centerline;stroke:none;fill:black;">118444(12)</text> <rect x="0" y="-10.125" width="1.5" height="0.75" style="stroke-width: +0.010267;"/> <rect x="0" y="-10.875" width="1.5" height="0.75" style="stroke-width: +0.010267;"/> <rect x="0" y="-11.625" width="1.5" height="0.75" style="stroke-width: +0.010267;"/> </g> </svg>

For more on visualizing complex data structures, please see Answer: How can I visualize my complex data structure?

A List of Hash Resources


Chapter 3 in Beginning Perl by Simon Cozens (PDF)

Chapter 5 of Picking Up Perl by Bradley M. Kuhn (PDF)

Section 2.3 in Impatient Perl by Greg London (PDF)

Steve's place - Perl Tutorial, by Steve Cook (archive)

Perl Training Australia's superlative materials:

What is Scalar Context? by Dominus

Understand References Today by Dominus

Hashes, as explained in PerlGuts Illustrated, by Gisle Aas How Hashes Really Work, by Abhijit Menon-Sen

Effective Perl: Intermediate and Advanced Topics contains a wealth of information, not limited to hashes, but also including several pages on Joseph N. Hall's PErl Graphical Structures (PEGS).

Uri Guttman's tutorial on AUTOVIVIFICATION

PerlMonks Tutorials:

the basic datatypes, three, by root

Hash Keys (strings or numbers?), by robot_tourist

The Uniqueness of hashes, by injunjoel

Multidimensional Arrays, by CharlesClarkson

references, by busunsl

References quick reference, by tye

Object Serialization Basics, by chromatic

PerlMonks Categorized Questions and Answers:


Other PerlMonks Nodes:

Extracting array of hashes from data by nysus

how to avoid mis-spelling hash keys?, by Gorilla

Perl Internals: Hashes, by Kozz

help with hashes, by Anonymous Monk

The Bad, the Ugly, and the Good of autovivification, by tlm

the third item on tye's scratchpad is a hash intro

Autovivification trick, by blazar


perlfaq4: Data Manipulation - Manipulating numbers, dates, strings, arrays, hashes, and miscellaneous data issues



perlreftut }

perldsc    }Thanks, wfsp!

perllol     }


Obligatory Google



Chapters 5 and 15 of Learning Perl by Randal L. Schwartz and Tom Phoenix

Pages 10-12 and 76-78 of Programming Perl, 3rd Ed., by Larry Wall, Tom Christiansen, Jon Orwant

Chapter 5 of the Perl Cookbook, 1st Ed., by Tom Christiansen, Nathan Torkington

Update: This is only a beginning. I noticed a lack of material on hashes in the Tutorials section, and thought I could contribute something, even though it might be one step at a time...

Update(s): Thanks to wfsp for pointing out... I forgot the perldocs!

2005-07-02: added perlfaq4, perlref, 125289, 137108, 69927, 224434

2005-07-06: several links per section; too lazy to enumerate

2005-07-07: added hashes, tye's scratchpad, and some code

2005-08-07: added info on FakeHash, including code and graphics

2005-09-12: fixed several broken links, brought to my attention by Hue-Bond (Thanks!)

2005-12-18: added link to The Uniqueness of hashes, by injunjoel

2006-03-25: re-arranged code and references in more logical order; added anchors; added pic and SVG output and info on pic2plot

2006-03-26: added link to Object Serialization Basics, by chromatic

2006-08-13: added link to Autovivification trick, by blazar

2008-12-11: fixed several broken links, brought to my attention by pmonk4ever (Thanks!); also fixed a few b0rked tags



p l a n e t s c a p e

In reply to Not Exactly a Hash Tutorial by planetscape

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