《Perl 语言入门习题答案》 2 .1 2 练习 1 、写一个程序，计算半径为12.5的圆的周长。圆周长等于2π（π约为3.1415926）乘以半径。答案为78.5。 -----------------------/home/confish/perl/girth #!/usr/bin/perl -w #this program calculate a circle's girth #****************** $r=12.5; $g=12.5*2*3.1415; print "the girth of the circle is $g\n"; -----------------------/home/confish/perl/girth 2 、修改上述程序，用户可以在程序运行时输入半径。如果，用户输入12.5，则应得到和上题一样的结果。 -----------------------/home/confish/perl/girthpro #!/usr/bin/perl -w #a better one to calculate girth #****************** print"enter the radius of the circle\n"; chomp($r=); if($r>0) { print"the girth of the circle is ".$r*2*3.1415."\n"; } else { print"nonavailable!\n"; } -----------------------/home/confish/perl/girthpro 3 、修改上述程序，当用户输入小于0 的数字时，程序输出的周长为0，而非负数。 -----------------------/home/confish/perl/girthzero #!/usr/bin/perl -w #calculate the girth and print 0 when the radius is lower than 0 #****************** print"enter the radius of the line\n"; chomp($r=); if($r>0) { print"the girth of the circle is $r*2*3.1415\n"; } else { print"the girth of the circle is 0\n"; } -----------------------/home/confish/perl/girthzero 1 、2 、3 ：（一起实现的） #!/usr/bin/perl -w $pai=3.141592654; print "Please Input Radius:"; $r=; if ( $r lt 0 ){ print "The circumference is 0\n"; }else{ $l=$r*2*$pai; printf "The circumference is %.1f\n",$l; } 4 、写一个程序，用户能输入2 个数字（不在同一行）。输出为这两个数的积。 -----------------------/home/confish/perl/product #!/usr/bin/perl -w #print the two number's product #******************print"enter the two numbers:\n"; chomp($m=); chomp($n=); print"the product of the two numbers are ".$m*$n."\n"; -----------------------/home/confish...
