I've also been scratching my head over that leading space. The only thing I can think of is that he really wrote something like:

($BKSIC_MODEL[$i] = substr ($line, 3, 7)) =~ m/^\s*(.*)\s*$/;
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(which would simply capture the substr result and throw away the result of the pattern match)

... instead of the line he posted here:

($BKSIC_MODEL[$i]) = substr ($line, 3, 7) =~ m/^\s*(.*)\s*$/;
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(which should not capture the leading space)

buckaduck