You're not reading to EOF.

This: 

my $s1 = <STDIN>;

[download]

reads exactly one line. Since $/ is "\n" (see perlvar), your line ends at "\n".

If you want to read by line and get more than one line, I suggest some sort of iteration. Perhaps a while loop.

The most common idiom for reading a whole file line by line in Perl is: 

while ( <$filehandle> ) {
    # do something
}

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In your case, that'd be: 

while ( <STDIN> ) {
    # do something
}

[download]

There's really nothing mysterious going on. All of this is well-documented and widely known.

In reply to Re: read through \x0a in data piped via STDIN by mr_mischief
in thread read through \x0a in data piped via STDIN by How09

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