问基本perl代码分解

EN

#!/usr/bin/perl
@lines = `perldoc -u -f atan2`;
foreach (@lines) {
s/\w<([^>]+)>/\U$1/g;
print;
}

s/\w<([^>]+)>/\U$1/g;

ATAN2 ARCTANGENT TAN TANGENT <--- X<atan2> X<arctangent> X<tan> X<tangent>

MATH::TRIG::TAN <------- C<Math::Trig::tan>

perldoc -u -f atan2
=over 8

=item atan2 Y,X
X<atan2> X<arctangent> X<tan> X<tangent>

Returns the arctangent of Y/X in the range -PI to PI.

For the tangent operation, you may use the C<Math::Trig::tan>
function, or use the familiar relation:

    sub tan { sin($_[0]) / cos($_[0])  }

The return value for C<atan2(0,0)> is implementation-defined; consult
your atan2(3) manpage for more information.

=back

[/cygdrive/c/Users/Documents/learn_perl]$ ./hello_world.pl 
=over 8

=item atan2 Y,X
ATAN2 ARCTANGENT TAN TANGENT

Returns the arctangent of Y/X in the range -PI to PI.

For the tangent operation, you may use the MATH::TRIG::TAN
function, or use the familiar relation:

    sub tan { sin($_[0]) / cos($_[0])  }

The return value for ATAN2(0,0) is implementation-defined; consult
your atan2(3) manpage for more information.

=back