Anonymous Monk is right, this most likely has something to do with what $l_Name_ref refers to. Most likely, this is a capture variable that then gets reset by the next match operation:

#!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>
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I doubt that the intent is really to pass around a reference to $1, as that has the described side effects. It's likely better to pass a reference to a copy of $1, as in Attempt 2.