Re: Basic Regular expression

by Marshall (Canon)
 on Feb 09, 2017 at 16:39 UTC ( #1181548=note: print w/replies, xml ) Need Help??

in reply to Basic Regular expression

from http://perldoc.perl.org/perlre.html:
By default, a quantified subpattern is "greedy", that is, it will match as many times as possible (given a particular starting location) while still allowing the rest of the pattern to match. If you want it to match the minimum number of times possible, follow the quantifier with a "?" . Note that the meanings don't change, just the "greediness":
\$1 leaves space so that the other terms can match.

Update, consider:

```my \$x = "This is Perl";
\$x =~/^((.+)(e|r)(.*))\$/;
print "1={\$1}  2={\$2}  3={\$3}  4={\$4}\n";
# 1={This is Perl}  2={This is Pe}  3={r}  4={l}

my \$x = "This is Perl, nice Perl";
\$x =~/^((.+)(e|r)(.*))\$/;
print "1={\$1}  2={\$2}  3={\$3}  4={\$4}\n";
# 1={This is Perl, nice Perl}  2={This is Perl, nice Pe}  3={r}  4={l}
A small update, I changed \$a to \$x in the above code. In Perl, \$a and \$b are special variables used for among other things in sort functions. Normal user code should not use these variables except in their strange special cases. So something like \$x and \$y is better. In the above code using \$a wouldn't matter, but I changed it anyway to point out that this is a bad habit that can lead to problems in longer programs. Just something to watch out for if you code in other languages that don't have special meanings for a or b.

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Re^2: Basic Regular expression
by skkeni04 (Initiate) on Feb 13, 2017 at 03:33 UTC
Thanks, got it!

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