#!/usr/bin/perl -l
$_=pop;{print;my$b;$b.=$1+$2>9?$1+$2-9:$1+$2while s/(.)(.)/$2/;($_=$b)&&redo}
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#!/usr/bin/perl -l
sub a{print$_=pop;my$b;$b.=$1+$2>9?$1+$2-9:$1+$2while s/(.)(.)/$2/;$b&&a($b)}a pop
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#!/usr/bin/perl -l
print$_=pop;while(/../){my$b;$b.=$1+$2>9?$1+$2-9:$1+$2while s/(.)(.)/$2/;print$_=$b}
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#!/usr/bin/perl -l
print$a=pop;while($a>9){my$b;while($a=~s/(.)(.)/$2/){$t=$1+$2;$t=~s/(.)(.)/$1+$2/e if$t>9;$b.=$t}print$a=$b}
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#!/usr/bin/perl -l
print$a=pop;while($a>9){@b=split'',$a;my@c;for(0..$#b-1){$t=$b[$_]+$b[$_+1];$t=~s/(.)(.)/$1+$2/e if$t>9;push@c,$t}$a='';map$a.=$_,@c;print$a}
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