TWTOWTDI :)

perl -lne '$s=$_; END{ print "OK" if $s=~/^T/ }' /tmp/foo
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Though you might want exit codes instead, depending on what's calling this

perl -ne '$s=$_; END{ exit($s=~/^T/ ? 0 : 1) }' /tmp/foo
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Or, using File::Tie:

perl -MTie::File -e 'tie @f, "Tie::File", shift; exit 1 unless $f[-1] 
+=~ /^T/' /tmp/foo
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Or, using File::ReadBackwards (untested):

perl -MFile::ReadBackwards -e 'exit 1 unless File::ReadBackwards->new(
+shift)->readline =~ /^T/' /tmp/foo
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