I'm not sure why you think it's strange behaviour; it seems logical to me.

You are putting $0 (the name of the current file) into @ARGV, and then reading from that file.  When you close the file with close ARGV, you've already read one line, which is in $_.  So when you do:

print '.',$_;
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you are simply printing out a period '.', concatenated with the first line of the Perl script itself.

Try taking out the line close ARGV; and the whole program will be printed:

#!/usr/bin/perl -w
use strict; use warnings;
#prints one line and bails out
@ARGV = ( $0 );
while (<>) {
    # close ARGV;
    print $_;
}

# Output
#!/usr/bin/perl -w
use strict; use warnings;
#prints one line and bails out
@ARGV = ( $0 );
while (<>) {
        # close ARGV;
        print $_;
}
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