Hi, not much mystery to sleep ...

 perl -Mstrict -wlE '
 my @x = qw/ a b c d e f g h i j k l m n /;
 my $count = 0; 
 do { sleep 10 if $count++ == 10; say "$_ " . time } for @x
'
a 1509626827
b 1509626827
c 1509626827
d 1509626827
e 1509626827
f 1509626827
g 1509626827
h 1509626827
i 1509626827
j 1509626827
k 1509626837
l 1509626837
m 1509626837
n 1509626837
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