Thanks everybody about your kindly reply, following is my code according your replies, and the output which I want : 

#!/usr/bin/perl
use 5.010;
use strict;
use warnings;

my $port_name = 'sdm_yout_i[1]';
open my $fh,         "tt.txt"     or die $!;
while (<$fh>)
{
        if  (/\.([0-9a-z_]*?) \( \{.*?\Q$port_name\E .*?,/) {
            print '$port_name = ' ; say $port_name;
            print '$cell name = ' ; say $1;
    }
    
}

[download]

Outputs: 

 
$port_name = sdm_yout_i[1]
$cell name = sdm_yout_i

[download]

In reply to Re^2: Regular Expressions with varialbe with "[]" (Verilog) by herman4016
in thread Regular Expressions with varialbe with "[]" by herman4016

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