There's even Scalar::Readonly that allows you to modify readonly variables :)

#!/usr/bin/perl

use Scalar::Readonly 'readonly_off';

sub trim {
    for (@_) {
        readonly_off($_);
        s/^\s+//;
        s/\s+$//;
    }
}

for ('  foo  ', '  bar  ') {
    trim($_);
    print ">>$_<<\n";
}


__END__
>>foo<<
>>bar<<
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