If you cannot work out in your head what the substitution actually does (and it's not an easy thing if you are new to all this) then give it a try in some code. The lack of boilerplate in perl really helps when coding up trivial scripts for testing. eg:

#!/usr/bin/env perl 
use strict;
use warnings;

for my $word ('lama', 'aaron') {
    print "Word is $word\n";
    print "without /g the regex becomes: ";
    my $r = $word;
    $r =~ s/(.*?)[ab](.*?)/$1\[ab\]$2/;
    print "$r\n";

    print "with /g the regex becomes: ";
    $r = $word;
    $r =~ s/(.*?)[ab](.*?)/$1\[ab\]$2/g;
    print "$r\n";
}

[download]

Hopefully running this code will illustrate to you how the substitutions differ because of the /g modifier.

In reply to Re^5: Comparing Lines within a Word List by hippo
in thread Comparing Lines within a Word List by dominick_t

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.