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 scalar context, returns the number of times the
expression was true.
@foo = grep(!/^#/, @bar); # weed out comments
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or equivalently,
@foo = grep {!/^#/} @bar; # weed out comments
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Note that $_ is an alias to the list value, so it can be used to modify
the elements of the LIST. While this is useful and supported, it can cause bizarre results
if the elements of LIST are not variables. Similarly, grep returns aliases into the
original list, much as 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. This is
usually something to be avoided when writing clear code.
See also /map for a
list composed of the results of the BLOCK or EXPR.
