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=pod =head1 NAME Tie::Scalar::Substring - Tie strings to subranges of another string. =head1 SYNOPSIS my $s = "abcdefghijklmnop"; tie my $x, 'Tie::Scalar::Substring', \$s, 1, 5; tie my $y, 'Tie::Scalar::Substring', \$s, 2; =head1 DESCRIPTION If you need to define one or more strings in terms of being substrings of some other "fundamental" string, this module gives you exactly that. Strings so tied can be assigned; the effect is the same as assigning to lvalue C<substr>. Note that you can define a sub-string to have a certain specified length, or you can leave that parameter undefined, in which case the substring is "everything up to the end of the string", just as with C<substr>. =head1 CAVEATS The caveats are all the same as when assigning to lvalue C<substr>. You generally won't get useful results if a sub-string is defined as starting past the end of the underlying string. Assigning to one sub-string will (in general) affect the value of all other sub-strings, "magically". You may be surprised by the effect of assigning a value whose length is different from the defined length of the target string. For example: my $s = "abcdefghijklmnop"; tie my $x, 'Tie::Scalar::Substring', \$s, 1, 1; tie my $y, 'Tie::Scalar::Substring', \$s, 5, 1; print "before: '$x' '$y'\n"; $x = 'qu'; print "after: '$x' '$y'\n"; produces the following output: before: 'b' 'f' after: 'q' 'e' =head1 HISTORY 2005-07-16 jdporter Initial version. =cut use strict; { package Tie::Scalar::Substring; sub TIESCALAR { my( $pkg, $fund_str_sr, $ofs, $len ) = @_; # did you know that you can bless a reference # of type substr? defined $len ? ( bless \substr( $$fund_str_sr, $ofs, $len ), $pkg ) : ( bless \substr( $$fund_str_sr, $ofs ), $pkg ) } sub FETCH { my $self = shift; $$self } sub STORE { my $self = shift; $$self = shift; } sub LENGTH { my $self = shift; length( $$self ) } } # this block will be executed if you call this file as a script, # but not when it's require'd. It's essentially a unit test. unless ( caller(0) ) { my $s = "abcdefghijklmnop"; my $x; my $y; tie $x, 'Tie::Scalar::Substring', \$s, 5; #, 5; tie $y, 'Tie::Scalar::Substring', \$s, 7; #, 5; print "before:\n"; print "s=$s\n"; print "x=$x\n"; print "y=$y\n"; print "len(x)=", length($x), "\n"; $x = "quvwxyz"; print "\nafter:\n"; print "s=$s\n"; print "x=$x\n"; print "y=$y\n"; print "len(x)=", length($x), "\n"; } 1;

In reply to Tie::Scalar::Substring by jdporter

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