Re^2: Text matching repost

I later realised that instead of using

if (/$start/ or /$stop/) { print; }
[download]

I could just as well use (and more efficient too):

if ($&) { print; }
[download]

The meaning of $& is explained in perlvar as

The string matched by the last successful pattern match.

You can also use $MATCH if you use English;

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Re^3: Text matching repost by afoken (Chancellor) on Jun 18, 2012 at 14:24 UTC
I could just as well use (and more efficient too): `if ($&) { print; }` [download] Ummm, no. `$&` is one of the "ugly three" variables (the other two are $` and `$'`) that kill performance. From perlvar: The use of this variable anywhere in a program imposes a considerable performance penalty on all regular expression matches. To avoid this penalty, you can extract the same substring by using `@-`. Starting with Perl 5.10, you can use the `/p` match flag and the `${^MATCH}` variable to do the same thing for particular match operations. Apart from that, it may work for this special problem, but it does not work if `$&` evaluates to false: `perl -E '$x="a0b"; $x=~/0/; say $&; if ($&) { die "not reached!" } if + ($x=~/0/) { say "matched zero" }'` [download] Output: `0 matched zero` [download] Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]
Re^4: Text matching repost by Neighbour (Friar) on Jun 19, 2012 at 06:39 UTC
Good call, it shall be `if (scalar @-) { print; }` [download] then :)	[reply] [d/l]