Kolakoski

Score: 58.21 (pass)

#!perl
s/.?/$ARGV[1&pos]x$&||2/ge<999?do$0:print/(.{${\pop}})/,$/

Score: 58.22 (pass)

#!perl -l
s/.?/$ARGV[1&pos]x$&||2/eg<500?do$0:print/(.{${\pop}})/

Score: 60.21 (pass)

#!perl -l
{s/.?/$ARGV[1&pos]x$&||2/eg>999||redo}print/(.{${\pop}})/

Score: 63.22 (pass)

#!perl -l
print map{-@_+push@_,($:=$ARGV[$_%2])x($_[$_]||$:)}0..-1+pop

Score: 65.25 (pass)

#!perl -l
print map{-$#_+push@_,($x=$ARGV[~$_&1])x(shift@_||$x-1)}1..pop