$_ = '       blee blah    ';
s/\s*(.*?)\s*/$1/;
print "matched '$&'; retained '$1'; str is '$_'\n";

##</code><code>##

matched '       '; retained ''; str is 'blee blah    '

##</code><code>##

s/^\s+//; 
s/\s+$//;

##</code><code>##

[matt@blade8 matt]$ perl -MBenchmark -e '@list1 = @list2 = map { " "x rand(100) . "some text" . " "x rand(100)  } 1 .. 100; timethese( 100_000, { single_regexp => sub { return map {  s/^\s*(.+?)\s*$/$1/; $_ } @list1 }, dual_regexp => sub { return map { s/^\s+//; s/\s+$//; $_ } @list2 }  } ); '
Benchmark: timing 100000 iterations of single_regexp, dual_regexp...
   single_regexp: 56 wallclock secs (56.04 usr +  0.00 sys = 56.04 CPU) @ 1784.44/s (n=100000)
   dual_regexp: 17 wallclock secs (18.63 usr +  0.00 sys = 18.63 CPU) @ 5367.69/s (n=100000)