grep - locate elements in a list test true against a given criterion
grep BLOCK LIST
grep EXPR,LIST
This is similar in spirit to, but not the same as,
grep(1) and its relatives. In
particular, it is not limited to using regular expressions.
Evaluates the
BLOCK or
EXPR for each element of
LIST (locally setting
$_ to each element) and returns the list value consisting of those elements for which the expression evaluated to
TRUE. In a scalar context, returns the number of times the expression was
TRUE.
@foo = grep(!/^#/, @bar); # weed out comments
or equivalently,
@foo = grep {!/^#/} @bar; # weed out comments
Note that, because $_ is a reference into the list value, it can be used to modify the elements of the array. While this is useful and supported, it can cause bizarre results if the
LIST is not a named array. Similarly, grep returns aliases into the original list, much like the way that a for loop's index variable aliases the list elements. That is, modifying an element of a list returned by grep (for example, in a
foreach, map() or another grep()) actually modifies the element in the original list.
See also map for an array composed of the results of the BLOCK or EXPR.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.