#!perl -w

sub foo {
    my( $ref )= @_;
    print "Before match: <$$ref>\n";
    'barring something else' =~ /bar/; # reset all capture variables
    print "After match: <$$ref>\n";

};

'blargh foo blargh' =~ /(foo)/;
foo( \$1 );

print "Attempt 2:\n";
'blargh foo blargh' =~ /(foo)/;
foo( \"$1" );

__END__
Before match: <foo>
Use of uninitialized value in concatenation (.) or string at q:\tmp.pl line 7.
After match: <>
Before match: <foo>
After match: <foo>