#! perl -slw
use strict;

my $re_term   = qr[[^,)]+?];
my $re_func   = qr[\w+\($re_term,$re_term\)];
my $re_concat = qr[concat\((?:($re_func),($re_term|$re_func))\)];

while(<DATA>) {
	s[^$re_concat$][$1 & $2];
	print;
}

__DATA__
concat(int2str(count,1),result)
concat(bit2str(count,'10'B),result)
concat(int2str(count,1),bit2str(count,'10'B))

##</code><code>##

c:\test>249976
int2str(count,1) & result

bit2str(count,'10'B) & result

int2str(count,1) & bit2str(count,'10'B)