The actual declaration for the given example would be:

my ($pattern, $number, @regexp, @compiled, $line);

And yes, you are correct, this is not a regex question, but IWTBTA.

.

.

(I Was Tempted By The Acronym)

Yes, it works this way, but you can improve it.

As a rule of thumb, use as small scopes as possible for variable declarartion, e.g. $pattern isn't used outside the foreach-loop (especially since $pattern is an alias to the current element of @compiled), and so it's useless to declare it "globally"

The same procedure with $line (although line is no alias, and the last content of line would stay in $line after the while block); if you write while( my $line = <> ) {, $line would only be usable within the while-loop-block, and you don't need to care if there is another $line somewhere outside the block which value is changed after the while loop)

use strict;
use warnings;

my $number   = shift; # first usage
my @regexp   = (); # initialize before first usage, my $regexp[$_] wou
+ldn't work
$regexp[$_]  = shift foreach (0..$number-1);
my @compiled = map qr/$_/, @regexp; # first usage

while( my $line = <> ) { # only in block
  foreach my $pattern (@compiled) { # only in block
    if( $line =~ /$pattern/ ) {
      print $line;
      last;
    }
  }
}
[download]

or the like

And I guess you can write the shift foreach-line in a better readable way:

my $number = shift( @ARGV        );
my @regexp = @ARGV[ 0..$number-1 ];
[download]