Kolakoski

Score: 77.18 (pass)

#!perl
$/=$ARGV[1-$_%2],$*.=$/x($2||$/),$*=~s/(.)(.?)/$2/,print$1for 1..pop;print'
'

Score: 79.17 (pass)

#!perl
$/=$ARGV[($_-1)%2],$*.=$/x($2||$/),$*=~s/(.)(.?)/$2/,print$1for 1..pop;print'
'

Score: 82.20 (pass)

#!perl -l
$/=$ARGV[$_%2],$*.=$/x(substr($*,$_,1)||$/)for 0..500;print substr$*,0,pop@ARGV

Score: 93.12 (pass)

#!perl -l
($/,$;,$.)=@ARGV;$*.=$/x(substr($*,$_,1)||$/),($/,$;)=($;,$/)for 0..$.;print substr$*,0,$.

Score: 98.17 (pass)

#!perl
($/,$;,$l)=@ARGV;$z.=$/x(substr($z,$i++,1)||$/),($/,$;)=($;,$/)for 1..$l;print substr($z,0,$l)."
"