1. BLOCK:
{} BLOCK as the part between blocks.

2. The conditional statement:
if (expression)   BLOCK;

if (expression)  
    BLOCK1
the else BLOCK2;

if (expression1)  
    BLOCK1;

elsif (expression2)     BLOCK2;
the else
      BLOCK3;

#inverted if statement
expression the if (test_expression);

involves the relationship between operator:
numeric value comparison:==, >, <, >=, <=,!=; With a numeric value comparison operators compare the string, string as 0;
string comparison: eq, gt, lt, ge, le, ne; (undef as false to handle) :
the logical operators, &&, | |, and! ; And, or, not, etc.

3. Cycle:
the while (expression)
BLOCK;
do

BLOCK
the while (expression);

the for (initialization; test; increment)
BLOCK;

foreach $each (@ list)
BLOCK;

4. Other

the last: the last time, out of the current BLOCK, down come after BLOCK of code.
next: this time, so far, this BLOCK to the next round.
label: similar to goto.
the last and next and usually if the horse statements or label used in combination, realize the jump.
exit statement: exit 0; End of the current Perl program, return to the OS;
note: no switch statement in Perl, use the if - else to imitate.


This concludes the body part