Some code to get you started.

use strict;
use warnings;

my $eq = '2+3x+7x(x+27)-6';
my @mult=(1);
my @pow=(0);
my @c;
# die "Not supported.\n" if /[^-+0-9x]/;
die "Not supported: '$1' \n" if $eq =~ /([^-+0-9x()]+)/; # as per Anom
+alousMonk's suggestion
print "Equation: $eq\n";
while($eq=~/([-+]?)(\d*)(x?)([)(]?)/g){
  next unless "$1$2$3$4";
  my $d = $2 || 1;
  $d *= -1 if $1 eq '-';
  if( $4 eq '(' ) {
    push @mult, $mult[-1]*$d;
    push @pow, $pow[-1]+1;
  } else {
    if( $3 ) {
      $c[1+$pow[-1]] += $mult[-1]*$d;
    } else {
      $c[$pow[-1]] += $mult[-1]*$d;
    }
  }
  if( $4 eq ')' ) {
    pop @mult;
    pop @pow;
  }
}
print "Summary: @c\n";
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