Perl functions: subroutines

[Wilbur]

Hi all, my first time here! Can someone assist me? i need to write a "simple" perl scripts to cancatenate two strings (preferably short DNA sequences) using the subroutine function? Mine doesnt print anything.Also need general hints on subroutines.I'm still new to perl (and programming in general!).

Here is the script I had writen:

#!/usr/bin/perl;
#subroutine to concatenate two strings of dna
#practicesubroutines1.txt

sub conc($);
print "enter the dna sequence1>>";
$dna1=<>;
print "enter dna sequence2>>";
$dna2=<>;
$newdna=conc($dna);
print "the new dna is $newdna\n";

sub conc($)
{
my $dna1=$_[0];
my $dna2=$_[0];
$dna="$dna1"."$dna2";
return $dna;
}

[jkmyoung]

Are you using <STDIN> ? eg
$dna1=<STDIN>;

Your function call has to pass both sequences in, eg:

$newdna=conc($dna1, $dna2);
....
sub conc{
$str = ""
foreach (@_) { $str = $str . $1;}
return $str;
}

[RonB]

jkmyoung,

Where did you get that $1 var? Did you mean to use $_?

[RonB]

Lets use a version that doesn't take unnecessary steps and is warnings and strict safe.

#!/usr/bin/perl;

use strict;
use warnings;
 
print "enter the dna sequence1>>";
chomp(my $dna1 = <>);

print "enter dna sequence2>>";
chomp(my $dna2 = <>);

my $newdna = conc($dna1, $dna2);
print "the new dna is $newdna\n";
 
sub conc {
    return join('', @_);
}

[Chendil]

Little modification to your code

# #!/usr/bin/perl;
# #subroutine to concatenate two strings of dna
# #practicesubroutines1.txt

 sub conc($$);
 print "enter the dna sequence1>>";
 $dna1=<>;
chomp($dna1);
 print "enter dna sequence2>>";
 $dna2=<>;
chomp($dna2);
 $newdna=conc($dna1,$dna2);
print "the new dna is $newdna\n";

 sub conc($$)
 {
 my $dna1=$_[0];
 my $dna2=$_[1];
 $dna="$dna1"."$dna2";
 return $dna;
 }