ID             Gene 
 
hsa-let-7a	KRAS 
hsa-let-7a	HMGA2 
hsa-let-7a	integrin beta(3) 
hsa-let-7a	caspase-3 
hsa-let-7a	PRDM1/Blimp-1 
hsa-let-7a	HMGA2 
hsa-let-7a	IGF-II 
hsa-let-7a	HMGA2 
hsa-let-7a	HMGA2 
hsa-let-7a	RAS 
hsa-let-7a	BCL2 
hsa-let-7a	RAS 
hsa-let-7a	MYC 
hsa-let-7a	CDC25A 
hsa-let-7a	CDK6 
hsa-let-7a	NF2 
hsa-let-7a	c-myc 
hsa-let-7a	RAS 
hsa-let-7a	RAS 
hsa-let-7a	NIRF 
hsa-let-7b	Cdc34 
hsa-let-7b	Dicer 
hsa-let-7b	KRAS 
hsa-let-7b	CCND1 
hsa-let-7b	CDC25A 
hsa-let-7b	CDK6 
hsa-let-7b	HMGA2 
hsa-let-7c	HMGA2 
hsa-let-7c	HMGA2 
hsa-let-7c	HMGA2 
hsa-let-7c	BCL2 
hsa-let-7c	RAS 
hsa-let-7c	CDC25A 
hsa-let-7c	CDK6 
hsa-let-7c	RAS 
hsa-let-7d	KRAS 
hsa-let-7d	HMGA2 
hsa-let-7d	BCL2 
hsa-let-7d	RAS 
hsa-let-7d	CDC25A 
hsa-let-7d	CDK6 
hsa-let-7d 	BDNF 
hsa-let-7d 	D3R 
hsa-let-7e	HMGA2 
hsa-let-7g	KRAS 
hsa-let-7g	HMGA2 
hsa-let-7g	Ras 
hsa-let-7g	HMGA2 
hsa-let-7g	CDC25A 
hsa-let-7g	CDK6 
hsa-miR-1	c-Met 
hsa-miR-1	calmodulin 
hsa-miR-1	Gata4 
hsa-miR-1	Mef2a 
hsa-miR-1	BCL2 
hsa-miR-1	Gata4 
hsa-miR-1	calmodulin 
hsa-miR-1	Mef2a 
hsa-miR-1	C/EBPa 
hsa-miR-1	FoxP1 
hsa-miR-1	HDAC4 
hsa-miR-1	MET 
hsa-miR-1	HCN4 
hsa-miR-1	FoxP1 
hsa-miR-1	HDAC4 
hsa-miR-1	MET 
hsa-miR-1	Cdk9 
hsa-miR-1	fibronectin 
hsa-miR-1	RasGAP 
hsa-miR-1	Rheb 
hsa-miR-1	MEF-2 
hsa-miR-1	nAChR 
hsa-miR-1	GAJ1 
hsa-miR-1	KCNJ2 
hsa-miR-1	HSP60 
hsa-miR-1	HSP70 
hsa-miR-1	Hand2 
hsa-miR-1	Kir2.1 
hsa-miR-100	Plk1 
...... 
(line cut)

ID                     Gene 
   
hsa-let-7a    KRAS,HMGA2,integrin beta(3),caspase-3,PRDM1/Blimp-1,HMGA2,IGF-II,HMGA2,HMGA2,RAS,BCL2,RAS,MYC,CDC25A,CDK6,NF2,c-myc,RAS,RAS,NIRF 
hsa-let-7b    Cdc34,Dicer,KRAS,CCND1,CDC25A,CDK6,HMGA2 
hsa-let-7c    HMGA2,HMGA2,HMGA2,BCL2,RAS,CDC25A,CDK6,RAS 
.........

foreach $var (@array) 
{ 
  ($key,$val) = split('\t',$var); 
  unless(defined($hash{$key})){ 
    $hash{$key}=$val; 
  } 
  else{ 
    $hash{$key}.=",$val"; 
  } 
} 
for (keys %hash) 
{ 
     print "\nkey:$_---Val:$hash{$_}\n"; 
}

#!/usr/bin/perl 
 
use 5.10.1; 
use strict; 
use warnings; 
 
my %gene; 
 
open my $fh, '<', 'genes.txt' or die "failed to open genes.txt $!"; 
 
 
while ( my $line = <$fh> ) { 
    chomp $line; 
    my($id, $gene) = split /\t/, $line; 
    push @{$gene{$id}}, $gene; 
} 
close $fh; 
 
for my $id (keys %gene) { 
    say "$id\t", join ',', @{$gene{$id}}; 
}

use strict; 
use warnings; 
 
my %hash; 
while (<>) { 
	push @{ $hash{$1} }, $2 if /(\S+)\s+(\S+)/; 
} 
 
local $" = ','; 
print "$_\t@{ $hash{$_} }\n" for sort keys %hash;

hsa-let-7a	KRAS,HMGA2,integrin,caspase-3,PRDM1/Blimp-1,HMGA2,IGF-II,HMGA2,HMGA2,RAS,BCL2,RAS,MYC,CDC25A,CDK6,NF2,c-myc,RAS,RAS,NIRF 
hsa-let-7b	Cdc34,Dicer,KRAS,CCND1,CDC25A,CDK6,HMGA2 
hsa-let-7c	HMGA2,HMGA2,HMGA2,BCL2,RAS,CDC25A,CDK6,RAS 
hsa-let-7d	KRAS,HMGA2,BCL2,RAS,CDC25A,CDK6,BDNF,D3R 
hsa-let-7e	HMGA2 
hsa-let-7g	KRAS,HMGA2,Ras,HMGA2,CDC25A,CDK6 
hsa-miR-1	c-Met,calmodulin,Gata4,Mef2a,BCL2,Gata4,calmodulin,Mef2a,C/EBPa,FoxP1,HDAC4,MET,HCN4,FoxP1,HDAC4,MET,Cdk9,fibronectin,RasGAP,Rheb,MEF-2,nAChR,GAJ1,KCNJ2,HSP60,HSP70,Hand2,Kir2.1 
hsa-miR-100	Plk1