Help with /g match option

[dolpho37]

All,

On page 191 of Perl Cookbook you find this code snippet:

$n = " 49 here";
$n =~ s/\G /0/g;
print $n;
00049 here

Under discussion is \G matching the last position by virtue of /g
match option being present. What I'm having a hard time understanding
is why the pattern '\G ' doesn't match the space between the '9' and
'h' of '49 here'. Can someone help me out? Thanks in advance.

Kind regards,
Dolpho37

 

[Jeff 'japhy' Pinyan]

[posted & mailed]

$n = " 49 here";
$n =~ s/\G /0/g;
print $n;

00049 here

Under discussion is \G matching the last position by virtue of /g
match option being present. What I'm having a hard time understanding
is why the pattern '\G ' doesn't match the space between the '9' and
'h' of '49 here'. Can someone help me out? Thanks in advance.

It's because \G HAS to match where /g left off, or else ^ if the regex
hasn't matched yet. So /\G / matches the FIRST space, the SECOND space,
and the THIRD space. But then /\G / can't match, because the character at
the location \G matches is a '4', not a ' '.