my $str = 'Internal Computing Department';
my $res = join '' , map {(split //,$_)[0]} split /\s/, $str;
# OR 
my $res = join '' , map { substr $_, 0 , 1 } split /\s/, $str;
# OR 
my $res;
$res .= $1 while ( $str=~m/(\S)\S+/g );

print $res;