PerlGrepExactMatch

Want to perform an exact match with Perl's grep function?

Perl's grep function is incredibly powerful. However, at first glance it can seem as if Regular Expressions are going to trip you up. For example, if you want to perform an exact match with data that might contain Regualr Expression special characters. For example, this looks like it might be a problem...

my @elements=("apple", "apple.", "apple1", "apple2", "banana");

 my @results=grep(/apple/,@elements);5

Here, @results will contain "apple", "apple.", "apple1" and "apple2". This can or course be avoided as follows:

my @results=grep(/^apple$/,@elements);

Which will only put "apple" into the results. But what if the search term contains metacharacters (like . * ? etc)? For this you need a non-regular expression version of grep. Here's an example:

my @results=grep( { "$_" eq "apple." } @elements);

Here, @results will only contain "apple.", because it's the only thing that matches exactly. The check is a simple string "eq" rather than a regular expression, so metacharacters aren't used. Rememeber, this won't work:

my @results=grep(/^apple.$/, @elements);

...becuase the "." will match any single character. You'll end up with "apple.", "apple1" and "apple2" in @results.

ALSO SEE: PerlTextSort