Kolakoski

Score: 57.14 (pass)

#!perl -l
print eval'($_.=chop()x$+.$ARGV[$|--])=~/$&(.)/,'x pop

Score: 57.16 (pass)

#!perl -l
print eval'($_.=chop()x$1.$ARGV[$|--])=~/$&(.)/,'x pop

Score: 57.18 (pass)

#!perl -l
s/.?/$ARGV[1&pos]x($&||1)/eguntil/.{$ARGV[2]}/;print$&

Score: 58.16 (fail)

#!perl -l
s/.?/$ARGV["@-"%2]x($&||1)/eguntil/.{$ARGV[2]}/;print$&