in reply to Concatenate every 5 lines of input with a comma.

Did you already check perlvar?

Look for $. and $\.

But I wonder how you produce values separated with ; (semicolon), when you used , (comma) in your code? ;))

Update: example added: 

#!/usr/bin/perl
# vi:ts=4 sw=4 et:
use strict;
use warnings;

while ( <DATA> ) {
    chomp;
    local $\ = $. % 5 ? ";" : "\n";
    print;
}

__DATA__
1
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Re^2: Concatenate every 5 lines of input with a comma.
by ikegami (Patriarch) on Jul 09, 2009 at 19:34 UTC
    As a one-liner: 
    perl -ple'$\ = $.%5 ? ";" : $/' infile > outfile

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    In-place: 

    perl -i.bak -ple'$\ = $.%5 ? ";" : $/' file

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    If it wasn't a one-liner, I wouldn't use $\ 

    while ( <DATA> ) {
    chomp;
    print $_, $.%5 ? ";" : $/;
}

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