~/$ cat tmp.pl
#!/usr/bin/perl
use strict;
use warnings;

open(my $customers, $ARGV[0])|| die "Couldn't open $ARGV[0] $!\n";
my %cust;
while(<$customers>){
	chomp;
	my @rec=split(/\s+/, $_);
	push @{$cust{$rec[1]}->{time}},$rec[0];
	push @{$cust{$rec[1]}->{location}},$rec[2];
}

for my $cust (sort keys %cust){
	print "$cust: ",join(" ",@{$cust{$cust}->{time}})," : ",join(" ",@{$cust{$cust}->{location}}),"\n";
}
~/$ perl tmp.pl tmp.dat 
a: 12:10 12:13 : america australia
b: 12:11 2:30 : bombay bhutan
c: 12:12 : calcutta
n: 3:40 : neterland