You may find this an interesting starting point:

use strict;
use warnings;
my $x = "3 _ 4"; #in polar form.. 3 is mag and 4 is angle
my $y = "1i2"; #in rectangular form

print join ", ", constructComplex ($x);
print "\n" . join ", ", constructComplex ($y);

sub constructComplex
{
my $value1 = shift;
my @construct;
my ($a, $Form, $b) = $value1 =~ /([-+e.\d]+)\s*([i_])\s*([-+e.\d]+)/;

return undef if ! defined $b;

$value1 = $_[0];
if ($Form eq '_')
  {
  #uses $value1 to pick out the magnitude and angle
  my ($magnitude, $angle) = ($a, $b);
  $construct[2] = $magnitude;
  $construct[3] = $angle;
  # Do da polar to rect conversion
  }
else
  {
  my ($real, $complex) = ($a, $b);
  $construct[0] = $real;
  $construct[1] = $complex;
  # Do da rect to polar conversion
  }
 
return @construct; 
}
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Ignoring undef related warnings it prints:

, , 3, 4
1, 2
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