Another alternative is:

sub zapwrap {
  my ($line, $next_line) = (@_);
  return undef unless $line =~ /^#(#+|=+)$/;
  my $c= quotemeta substr($1,0,1);
  return undef unless $next_line =~ /$c+/;
  return 1;
}
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though I prefer the one proposed by japhy. Also note that if the repeated character has special meaning in a regular expression, then you'd need to use \Q$1\E in japhy's version.

        - tye (but my friends call me "Tye")