I like AppleFritter’s approach. But, in the spirit of TMTOWTDI, here’s another, which builds the required regex via a subroutine call:

#! perl
use strict;
use warnings;

my %searches =
(
    bar => " bar  \n\n",
    foo => "  foo  c  \n",
);

for (sort keys %searches)
{
    print "$_: ", $searches{$_} =~ re($_) ? 'match' : 'no match', "\n"
+;
}

sub re
{
    qr{ ^ \s* $_[0] \s* $ }x;
}
[download]

Output:

23:06 >perl 1402_SoPW.pl
bar: match
foo: no match

23:06 >
[download]

Hope that helps,