in reply to write() removes trailing spaces
There is nothing strange. The following altered code demonstrates that your $c variable contains 13 chars , which you want displayed within 11 space holders (1+10). Two chars werer choped, as per your request .
format STDOUT = @<<<<@<<<<@<<<<<<<<<<END $a, $b, $c . $a = "a"; $b = "b"; $c = "c .bc"; print 'len=',length $c; write(STDOUT);
Produces this output:
len=13 a b c .END