my @list;
#Read first, ask questions later is probably not optimal for this
#Scope our variable, merge, read, and assign all at once
while(chomp(my $line = <NETLIST>)){
  #Save a match, substitution returns true iff we susbtituted
  if ($line =~ s/^\+//){
    #Append to previous line (last line in the array)
    $list[-1] .= $line;
  }
  else{
    #Save the line
    push(@list, $line);
  }
}
#Map is good, nice way to get all the newlines back
#join would work if you the file need not end in a newline
print map {"$_\n"} @list;
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=>

my @list;
while(chomp(my $line = <NETLIST>)){
  #Trinary is good ;-)
  $line =~ s/^\+// ? $list[-1] .= $line : push(@list, $line);
}
print map {"$_\n"} @list;
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=>

my @list;
#for is very perlish, so is using $_
chomp && $_ =~ s/^\+// ? $list[-1] .= $_ : push(@list, $_) for <NETLIS
+T>;
print map {"$_\n"} @list;
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--
perl -pe "s/\b;([mnst])/'\1/mg"