$ perl -E'
   sub f { say $1; "b"=~/(b)/; say $1; }
   "a"=~/(a)/;
   say $1; f(); say $1;
'
a
a
b
a

##</code><code>##

$ perl -E'
   sub f { say $_[0]; "b"=~/(b)/; say $_[0]; }
   "a"=~/(a)/; f($1);
'
a
b

##</code><code>##

/.../;
mysub("$1", "$2");
sub mysub {
   /.../;
   shift;
   shift;
}

##</code><code>##

my ($x, $y) =~ /.../;
mysub($x, $y);
sub mysub {
   /.../;
   shift;
   shift;
}

##</code><code>##

/.../;
mysub($1, $2);
sub mysub {
   my ($x, $y) = @_;
   /.../;
   $x;
   $y;
}