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perlman:perlfaq4

by root (Scribe)

on Oct 13, 1999 at 03:09 UTC ( #797=perlman: print w/replies, xml )

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perlfaq4

Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

The section of the FAQ answers question related to the manipulation of data as numbers, dates, strings, arrays, hashes, and miscellaneous data issues.

Data: Numbers

Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)?

Why isn't my octal data interpreted correctly?

Does perl have a round function? What about ceil() and floor()? Trig functions?

How do I convert bits into ints?

How do I multiply matrices?

How do I perform an operation on a series of integers?

How can I output Roman numerals?

Why aren't my random numbers random?

Why aren't my random numbers random?

Data: Dates

How do I find the week-of-the-year/day-of-the-year?

How can I compare two dates and find the difference?

How can I take a string and turn it into epoch seconds?

How can I find the Julian Day?

Does Perl have a year 2000 problem? Is Perl Y2K compliant?

Data: Strings

How do I validate input?

How do I unescape a string?

How do I remove consecutive pairs of characters?

How do I expand function calls in a string?

How do I find matching/nesting anything?

How do I reverse a string?

How do I expand tabs in a string?

How do I reformat a paragraph?

How can I access/change the first N letters of a string?

How do I change the Nth occurrence of something?

How can I count the number of occurrences of a substring within a string?

How do I capitalize all the words on one line?

How do I strip blank space from the beginning/end of a string?

How do I extract selected columns from a string?

How do I find the soundex value of a string?

How can I expand variables in text strings?

What's wrong with always quoting "$vars"?

Why don't my <<HERE documents work?

Data: Arrays

What is the difference between $array[1] and @array[1]?

How can I extract just the unique elements of an array?

How can I tell whether a list or array contains a certain element?

How do I compute the difference of two arrays? How do I compute the intersection of two arrays?

How do I find the first array element for which a condition is true?

How do I handle linked lists?

How do I handle circular lists?

How do I shuffle an array randomly?

How do I process/modify each element of an array?

How do I select a random element from an array?

How do I permute N elements of a list?

How do I sort an array by (anything)?

How do I manipulate arrays of bits?

Why does defined() return true on empty arrays and hashes?

How do I process an entire hash?

Data: Hashes(Associative Arrays)

What happens if I add or remove keys from a hash while iterating over it?

How do I look up a hash element by value?

How can I know how many entries are in a hash?

How do I sort a hash (optionally by value instead of key)?

How can I always keep my hash sorted?

What's the difference between "delete" and "undef" with hashes?

Why don't my tied hashes make the defined/exists distinction?

How do I reset an each() operation part-way through?

How can I get the unique keys from two hashes?

How can I store a multidimensional array in a DBM file?

How can I make my hash remember the order I put elements into it?

Why does passing a subroutine an undefined element in a hash create it?

How can I make the Perl equivalent of a C structure/C++ class/hash or array of hashes or arrays?

How can I use a reference as a hash key?

How can I use a reference as a hash key?

Data: Misc

How do I handle binary data correctly?

How do I determine whether a scalar is a number/whole/integer/float?

How do I keep persistent data across program calls?

How do I print out or copy a recursive data structure?

How do I define methods for every class/object?

How do I verify a credit card checksum?

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