Rather than the series of if { ... } elsif { ... } ... tests you could use a hash table to look up the base and use it as the fourth argument to substr to replace the original.

$ perl -Mstrict -Mwarnings -E '
my $dna        = q{AAGGTTCC};
my %compLU     = (
   A => q{T},
   T => q{U},
   G => q{C},
   C => q{G},
   );
my $complement = $dna;

for my $idx ( 0 .. length( $complement ) - 1 )
{
    substr $complement, $idx, 1, $compLU{ substr $complement, $idx, 1 
+};
}

say $dna;
say $complement;'
AAGGTTCC
TTCCUUGG
$

[download]

I hope this is of interest.

Cheers,

JohnGG

In reply to Re: Trying to use substring to find a reverse complement in DNA, by johngg
in thread Trying to use substring to find a reverse complement in DNA, by tryingnottofailmytes

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.